Just to confirm: this is meant for people that have basic understanding (at least) of electrical systems - single/tri phase, what is a transformer with a center tap, etc.
On the picture above X2 and X3 will be the center tap on my transformer. And yes - it is using a commercial 3P 480V which I installed at my business location. The HPWC is documented to work on 240-250V max, but on it's box's label it says it is a 277V device. So theoretically:
(I haven't tested this!!!)
You can hook it up on one of the legs of the 3P 480V (it should be 277V or 280V). In all types of connections that are documented in the manual you have to have a ground connected and it has to be the middle point (L1-G and L2-G should measure half the L1-L2). As far as I know there is no center tap on regular 3P 480V installation so HPWC has to be switched to L-N-G mode by flipping both DIP switches up. Then neutral(N) and ground(G) should be one and the same (in the breaker panel). This last setup I only assume it would work (since not documented by Tesla).
(My current complete and working setup)
Now what I have up and running - I got 2 legs of the 3P 480V (they measure 480V between) and ran them 200ft to my transformer (see the pic above). I had my transformer's entry set up for 432V, so the secondary side is ~270V that goes into a 120/240V single phase breaker panel. I use this panel for the tesla charger, so I am not worried about "overvolting" other devices that require 120V or 240V. I use the center tap (X2 and X3) together with X1 and X2 to connect respectively N and L1 L2 on the panel. Bottom line - I have my HPWC connected to 268V and charging with 48A my Model 3. The DIP switches are set up to DOWN-UP as shipped from factory.
Pros and cons of both:
1) 1 leg of a 3P 480V (assuming this will work)
Pros: Less initial cost (no transformer), no power loss from the transformer
Cons: You need bigger (lower AWG) cables or the voltage drop will be significant.
2) 2 legs of 3P 480V with transformer
Pros: Lower gauge cables and you can install further away from your 480V panel
Cons: Cost of transformer, operational power loss in the transformer.
I only charged once in my current setup and can't provide numbers and stats yet, but my goal was to charge as fast as I can. Even if it cost more to install it.
Disclaimer: This is not a tutorial or anything like that. I share my experience and I am not liable for any damage you might cause.